1. Field of the Invention
The present invention relates to a radio communication system, a radio communication apparatus, and a radio communication method that are capable of reducing the proportion of the overhead of a data frame.
2. Description of the Related Art
In a conventional radio communication system such as a wireless LAN (for example, IEEE 802.11), a tradeoff relationship is generally established between communication reception quality of a radio signal and possible transmission rate. Accordingly, such a radio communication system has a problem that, as the communication reception quality of a radio signal is deteriorated, transmission efficiency decreases more significantly than in the case of a cable communication system.
Specifically, in such a radio communication system, there is a problem that the proportion of a header, that is, the proportion of the overhead, becomes large in a data frame, when the transmission rate decreases with the deterioration of communication reception quality. Here, the data frame consists of payload used for transmitting and receiving user data, and the header including control information and the source and destination addresses.
In view of the above problem, a method of omitting transmission of information included in the header has been proposed (for example, in Japanese Patent Application Publication No. 2004-48115 (p. 11 and FIG. 4 of the patent document)) as means for reducing the proportion of the overhead of a data frame. Specifically, control information (such as information on communication parameter setting) included in a header is transmitted once in every predetermined number of (for example, three) data frames, instead of every single data frame. By means of this transmission method, it is possible to decrease information amount to be transmitted by using headers, and thereby to decrease the proportion of the overhead.
In recent years, along with development in radio communication technology, transmission rate, that is, channel capacity, in radio communication systems has been increasing. A widely known scheme for such a recent radio communication system is “High Capacity-Spatial Division Multiple Access (HC-SDMA) WTSC-2005-032 (ATIS/ANSI),” and iBurst (registered trademark) is provided as a radio communication system conforming to this scheme.
In addition, the increase in transmission rate has led to an ongoing discussion of the use of IEEE 802.2 LLC or the combination of IEEE 802.2 LLC and IEEE 802.3 (Ethernet, registered trademark), which are de facto standards in cable communication systems, as an upper layer protocol of the radio communication system.
However, even in the radio communication system, which is capable of providing high transmission rate, transmission rate decreases if the communication reception quality of a radio signal is deteriorated. Moreover, the proportion of the overhead in a data frame further increases in the case of using the above standards, IEEE 802.2 LLC and IEEE 802.3, as an upper layer protocol of the radio communication system.
To solve these problems, it is conceivable to use the above-described method of omitting transmission of information included in a header, for example. However, the method achieves only the reduction in the number of transmissions of control information (such as information on communication parameter setting). Hence, the method has a problem that it is not possible to omit transmission of the source and destination addresses, specifically, the MAC address (total 12 bytes) defined by IEEE 802.3 and the like, of a data frame.